Field of the Invention
The present invention relates to an image reading apparatus.
Description of the Related Art
Known as an example of a conventional image reading apparatus is an image reading apparatus that includes a platen glass, a guide member, a line sensor unit, and a coil spring. The platen glass supports a sheet by a front surface of the platen glass. The guide member is capable of reciprocating movement in a sub-scanning direction along a reverse surface of the platen glass, in a state of holding the line sensor unit. The line sensor unit has a reading surface and a plurality of optical sensor elements, and these elements are housed in a box-shaped housing. The reading surface includes a selfoc lens array and the like, and faces the platen glass. The optical sensor elements are each aligned in a main scanning direction.
Generally, the line sensor unit has a substrate. The substrate is held inside the housing in a state of facing the reading surface from an opposite to the platen glass. That is, the substrate is disposed in a bottom part of the housing, and a back of the substrate is covered by the housing. Moreover, each of the optical sensor elements is installed in a circuit board provided on a surface of the substrate.
The guide member includes a facing surface. The facing surface faces a back surface of the line sensor unit, specifically a back surface of the housing, from an opposite to the reading surface. The coil spring biases the line sensor unit in a first direction which is a direction approaching the platen glass. The coil spring is disposed such that its one end makes a contact with the facing surface of the guide member and its other end makes a contact with the back surface of the line sensor unit.
In the conventional image reading apparatus which is of the above-described configuration, the line sensor unit held in the guide member moves in the sub-scanning direction along the platen glass, in a state of being biased toward the platen glass by the coil spring, below the sheet supported by the platen glass. As a result, an image of the sheet supported by the front surface of the platen glass is read by the line sensor unit.